In microelectromechanical systems (MEMS), rotating hinges may be produced by etching a silicon substrate to form long, narrow beams. In the context of MEMS, as well as in the present description and in the claims, a “long, narrow” element has transverse dimensions (i.e., dimensions measured transversely to the longitudinal axis of the element) that are less than one tenth of the length of the beam. Such hinges are used, inter alia, in scanning micromirrors, such as those described, for example, in U.S. Pat. No. 7,952,781, whose disclosure is incorporated herein by reference. This patent describes a method of scanning a light beam and a method of manufacturing, which can be incorporated in a scanning device.
As another example, U.S. Patent Application Publication 2012/0236379 describes a LADAR system that uses MEMS scanning. A scanning mirror includes a substrate that is patterned to include a mirror area, a frame around the mirror area, and a base around the frame. A set of actuators operate to rotate the mirror area about a first axis relative to the frame, and a second set of actuators rotate the frame about a second axis relative to the base.
As yet another example, U.S. Patent Application Publication 2013/0207970, whose disclosure is incorporated herein by reference, describes a micromirror that is produced by suitably etching a semiconductor substrate to separate the micromirror from a support, and to separate the support from the remaining substrate. After etching, the micromirror (to which a suitable reflective coating is applied) is able to rotate in the Y-direction relative to the support on spindles, while the support rotates in the X-direction relative to the substrate on further spindles. (Such a support is also referred to as a gimbal, and the spindles are a type of hinges.) The micromirror and support are mounted on a pair of rotors, which are suspended in respective air gaps of magnetic cores. An electrical current driven through coils wound on the cores generates a magnetic field in the air gaps, which interacts with the magnetization of the rotors so as to cause the rotors to rotate or otherwise move within the air gaps.
As an alternative to the sorts of etched silicon hinges described above, Fujita et al. describe hinges made from polymeric material, in “Dual-Axis MEMS Mirror for Large Deflection-Angle Using SU-8 Soft Torsion Beam,” Sensors and Actuators A 121 (2005), pages 16-21. This article describes a MEMS galvano-mirror with a double gimbal structure having soft torsion beams made of the photosensitive epoxy resin SU-8. This approach is said to give large deflection angles (over ±40°) for small driving power.